A fluorescent switch sensor for detection of anticancer drug and ctDNA based on the glutathione stabilized gold nanoclusters

Abstract A facile and sensitive fluorescence switch sensor for the detection of both anticancer drug and calf thymus DNA (ctDNA) was developed based on glutathione stabilized gold nanoclusters by using mitoxantrone as both the fluorescence quencher to gold nanoclusters and the intercalating agent to ctDNA. The fluorescence of gold nanoclusters can be effectively quenched by MTX because of the absorption of MTX on the surface of gold nanoclusters and the subsequent occurring photoinduced electron transfer process from gold nanoclusters to MTX. As for possessing large conjugated system, MTX intercalates into the groove of duplex helix DNA. And the process efficiently promotes the separation of MTX from the surface of gold nanoclusters, which induces the enhanced fluorescence signal of the sensor. The fluorescence quenching effect was mainly concentration dependent, which was used to determine anticancer drug MTX. The fluorescent response of MTX detection was in the linear range from 0.1 μM to 6 μM with the detection limit of 20 nM. The restored fluorescence intensity was directly proportional to the concentration of ctDNA in the range of 0.5–8 μg/mL and a low detection limit of 0.1 μg/mL. The proposed method was applied for the detection of ctDNA in real samples with satisfactory results.